30 malignanciesis well documented,5?2-55 but that with other less well-defined agingcriteria is not clearcut. Beebe et al.,°> reporting on 1300 deaths from 1950 to 1966 among 8200 exposed Japanese, stated: “Once cancer is removedfrom thelist of natural causes, mortality appears to bear norelation to radiation dosage. In none of the 4 time periods is there evidence of general increase in mortality that one might expect from the hypothesis of accele: ated aging.” Since the underlying mechanisms of ordinary agingare not clearly defined, it is difficult to compare radiation effects with the aging process and to recognize their interaction. Studies of longevity in the relatively small Marshallese population under observation do not provide any evidenceof a possiblelife-shortening effect of radiation. At this time the average age at death in the Rongelap exposed groupis 64 years comparedwith 65 in the unexposed population, and 61 among the unexposed Uurik people. The differences are notsignificant. Numerousempirical studies concerned with possible radiation-induced aging effects have been carried out on the Japanese survivors®2-5§ and on the Marshallese.§:!2-15.57-61 Qn several occasions Rongelap people were given a battery of nonspecific tests for aging similar to those used in the Japanese studies.§:12-13 Some of these tests were based on subjective assessment, on a 0 to 4+ scale, of items such as greyness of hair, arcus senilis, senile changesin the skin, balding,etc., but most involved direct measurements of items such as skin looseness, skin elasticity (skin caliper), visual accom- modation, visual acuity, hearing (audiometric), blood pressure, neuromuscular function(light exunction test), hand strength (dynamometer), vibra- tory sense (vibrometer), and lean body mass (whole-body potassium by gamma spectrographic analysis). Comparison of these values in the exposed and unexposed Marshallese (Table 17) showednosignificant differences. The biological age scores (average percent score), plotted in Figure 23 for both groups, are about the same. 5. Immunological Studies Radiation is known to impair the immunological status of individuals soon after exposureif the dose is sufficient to producesignificant leukopenia. During the early period, though the acuteeffects on the Rongelap people included considerable depression of peripheral blood elements, comparison of the incidenceofinfections with that in the Utirik group gave no evidence of impaired immunity. Reduced immunological reserve may likely be a late effect of radiation exposure,® butit has not been observed conclusively in man. The development of leukemia and other malignancies following exposure may quite possibly be related to re- Table 17 Correlation of Criteria With Age and Radiation Exposure Correlation with age (r value) Correlation with radiation Percent Significance* ( ~) Grayness Arcussenilis Accommodation 0.87 0.83 0.81 +17.0 0.0 — 14.1 N.S. (0.70) N.S. (1.00) N.S. (0.11) Skin looseness 0.70 + 1.6 N.S. (0.82) Skin retraction 0.74 +73 NS. (0.68) Vibratory sense (M + F) 0.70** — 14(M), +24.6(F) Potassium (M +F) 0.41** —14.6(M), +10.6(F) Visual acuity Hearingloss Hand grip (M+F) Reaction time (M + F)(light extinction test) Systolic blood pressure Cholesterol Neuromuscular function (M + F) (handtally) Combined scoret *N.S. - not significant at 5% level. 0.69 0.67 0.67** 0.64** 0.55 0.39 0.36** 0.99 + 14.0 + 7.9 +13.8 (M), + 13.8 (F) — 2.0(M), ~ 10.5 (F —11.5 —17.2 + 3.2(M), +1.1 (F) + 7.0 **, values for males and females averaged. NS. (0.90, 0.20) N.S. N.S. N.S. N.S. N.S. (0.59) (0.40) (0.15, 0.18) (0.88, 0.55) (0.30) NS. (0.17, 0.22) N.S. (0.05) N.S. (0.85, 0.95) NS. (0.27) +Weighted accordingto 7 value.